Grinding device



Jan. 21, 1958 H. R. BILLETER GRINDING DEVICE 4 Sheets-Sheet 1 Filed Feb.15, 1956 @mW I WAN RAN IN VEN TOR.

ffsggg Ea Jan; 21, 1958 H. R. BILLETER 2,820,331

v V GRINDING DEVICE Filed Feb. 13, 1956 4 Sheets-Sheet 2 IN VEN TOR.

Jan. 21, 1958 R. BILLETER/ 2,820,331

GRINDING DEvIc I Filed Feb. 13. 1956 4 Sheets-Sheet 4 United StatesPatent 2,820,331 GRINDING DEVICE Henry Robert Billeter, Deerfield, Ill.,assignor to Ammcp Tools, Inc., North Chicago, 111., a corporation ofIllinois Application February 13, 1956, Serial No. 565,141

21 Claims. (Cl. 51-96) This invention relates to a grinding device andhas to do more particularly with a machine for grinding arcuatecontours, such as a grinder employed in dressingdown lined automotivebrake shoes, and a new and improved workpiece holder therefor. J

Grinding devices for forming arcuate contours, such as automotive brakeshoe grinders, commonly include a rotatable grinding element and aworkpiece holder mounted for pivotal movement of the workpiece relativeto the grinding element and in contact therewith whereby the grindingelement forms an arcuate surface on the workpiece or dresses down analready arcuate surface.

The pivot is adjustable toward and away from the grinding element todetermine the radius of the arcuate surface to be formed, but is adaptedto be fixed or held in one position of adjustment relative to thegrinding element during the grinding operation. In order to permitcontrol over the amount of materialremoved by the grinding operation,the workpiece holder is so constructed as to permit the workpiece to beadvanced or fed? toward the grinding element without disturbing thelocation of the pivot, and therefore without disturbing the pre-setradius of the arcuate surface.

In prior grinders and especially those employed in grinding automotivebrake shoes, the workpiece holder has been adapted to hold the workpiecesymmetrically and to feed the workpiece into a wheel-type grindingelement in such a manner that the surface to be ground is advancedtoward the grinding element in a direction perpendicular to the pivotaxis and along a line joining that pivot axis and the closest pointthereto on the grinding element. As the workpiece, for example, a brakeshoe, is fed into the grinding wheel and pivoted while in contact therewith so that material is removed from the shoe lining, the liningsurface is ground as to be uniformly arcuate about the center ofcurvature for the brake shoe, this center point coinciding with thepro-set pivot for the workpiece holder when the shoe is symmetricallypositioned in that holder. This operation is suitable and effective whendressing down or grinding the lining on a brake shoe adapted to be movedtoward and away from a brake drum along a radius bisecting the arc ofthe lining, and when a lined brake shoe of that type is ground asdescribed, it will properly engage the brake drum simultaneously alongall portions of the length of the lining. However, many present brakeshoes swing from one end about an anchor fixed within a brake drum, andpivot...

into engagement withthe'drum. For this type of shoe, merely grinding thelining to an arcuate contour does not necessarily insure thesimultaneous contact of all portions of the length of the lining withthe brake drum, since the brake shoe center of curvature will not alwayscoincide with the brake drum center of curvature at the instant ofcontact of the brake shoe lining with the brake drum. For this type ofbrake shoe, the important reference point for the arcuate surfacerelative t'o'the shoe is not the brake shoe centerof curvature, butrather the fixedanchor or pivot for the shoe, a point which has a fixedposition relative to the brake drum center of curvature.

The need for a fixed reference point for the brake shoe relative to thebrake drum axis is even more critical when grinding brake shoe liningsfor used fixed anchor brakes wherein the drums have been machined toremove scorings or to restore true cylindrical contours to the drums.These drums have larger internal diameters than originally, and theirbrake shoes no longer match those brake drum diameters as well astheydid prior to themachining. Any differential in arcuate contourbetween the two must be absorbed by the lining, the surface of whichmust be brought to the arcuate contour of the drum, not the shoe. I Y 1Since optimum braking efliciency can only be achieved by providing amaximum area of simultaneouscontact between lining and brake drum, aproper arcuate contour must be imparted to the lining in a mannersuchthat the contoured surface is properly positioned relative to thebrake drum and therefore to the fixed pivot or anchor of the shoe,rather than to the center of curvature of the brake shoe. This properdressing down of the lining of a fixed anchor brake shoe is bestaccomplished byadvancing that lined shoe into engagement with a grindingelement in a manner which simulates the movement of the brake shoe in abrake assembly.

An object of this invention is to provide a grinding device having anovel holder for pivotally advancing a workpiece into a grindingelement, which holder itself is pivotally supported on a carriage havingsliding rectilinear adjustment on a base toward and away from thegrinding element for exact adjustment of the position of the holderpivot axis relatively to the grinding element.

Another object is to provide a grinding device having a novel mechanismfor advancing a workpiece into a grinding element pivotally about anaxis which can be positioned to accommodate a standard range ofworkpiece sizes and configurations.

A further object is to provide an-automotive brake shoe grinder of theturntable type having-a novel work holder for advancing a fixed anchorbrake shoe .into a grinding element pivotally about the anchor recess ofthe; shoe itself, thus assuring a correct positioning of a predetermineda-rcuate contour on the lining of the shoe.

Another object is to provide an automotive brake'shoe grinder having aholder 'for pivotally advancing a brake shoe to be ground into agrinding element, which holder, is so designed and constructed as toeasily and accurately accommodate and hold any standard size and'configuration of brake shoe, and to correctly align the surface ofthebrake shoe lining with the grinding element for .proper dressing down ofthat surface.

A further object is to provide in a grinding device of the type having aworkpiece holder mounted on a turntable for oscillatory movement about aturntable axis adjustably fixed relatively to a grinding element, of apivotal advance mechanism by which the workpiece may be rapidly advancedto bring the workpiece into grinding relation with the grinding element,and by a simple manipulation secured in that advanced position andadvanced In finely-controlled manner therefrom, which holder by anothersimple manipulation may be rapidly retracted from any position to whichit has been advanced.

Yet a further object is to provide an automotive brake shoe grinderhaving a mechanism for pivotally advancing a fixed anchor brake shoeinto engagement witha grinding element in a manner similar to that inwhich the subject shoe pivots within its brake drum.

.A still further object is to provide a device for grind- Ing arcuatecontours, which device has a novel three-way means for associating aworkpiece with a grinding element so. that a radius of curvature for thearcuate con- 3 tour can be accurately and positively 'set,'the workpiecepivotally advanced into the grinding element without disturbing theradius of curvature set, and the workpiece swung through an arc ofengagement with the grinding element.

Another object is to provide a mechanism for pivotally advancing aworkpiece into engagement with a grinding element, which mechanism issimple and sturdy, free from any requirement of delicate adjustment, andwhich can be easily mounted on a standard grinding device of the slidingcarriage and turntable type.

Other objects and advantages of this invention will appear from adetailed description thereof taken in connection with the appendeddrawings, in which:

Figure 1 is a side elevational view of a brake shoe grinding deviceconstructed in accordancewith the principles of the present invention,certain of the parts being shown as broken away and others sectioned tomore clearly reveal the nature of the invention;

Fig. '2 is a perspective view of the brake shoe holder of the presentinvention mounted-on a turntable;

Fig. 3 is a fragmentary sectional view taken substantially on line 3-3of Fig. 1;

Fig. 4 is a fragmentary sectional view taken substantially on line 4-4of Fig. 2;

Fig. 5 is a rear elevational view of the brake shoe holder of Fig. 3,with a fragmentary diagrammatic illustration of the flange of a brakeshoe engaged by the chuck;

Fig. 6 is an enlarged fragmentary sectional view taken substantially online 6-6 of Fig. 3, with broken lines showing somewhat diagrammatically,and in exaggerated position for purposes of illustration, the relativeposition taken by the brake shoe when pivotally advanced about theanchor pin;

Fig. 7 is a sectional view taken on line 77 of Fig. 6;

Fig. 8 is a top plan view of the gauge of Fig. 6; and

Fig. 9 is a fragmentary top plan View showing the use of a modified formof anchor pin.

The grinding device of the present invention is especially well adaptedfor grinding to true arcuate contour the surfaces of linings attached toautomotive brake shoes of the fixed anchor type, and the device isdescribed here in in connection with such use for the purpose ofillustration. It is to be understood that the invention is not limitedto such an adaptation or use, and that the principles of this inventionmay be applied to other uses where generally similar results aredesired. 7

It will be understood that the workpiece holder of the present inventionis especially well adapted for use in a grinding device embodying abase, adjustable carriage and abrasive or grinding means similar tothose disclosed and claimed in my copending application Serial No.332,310, filed January 21, 1953, now Patent No. 2,734,319, grantedFebruary 14, 1956, to which reference may be had for a detaileddisclosure of the construction and operation of such elements.

Referring now particularly to Fig. 1 of the drawings, the grindingdevice includes a base 10 in the form of an elongate, rectilinearcasing-like member having a base flange 12 extending therearound fromwhich there extend upwardly and inwardly, preferably at a slight taper,a pair of side walls 14, a front wall 18 and a curved rear wall 20. Thetop wall of the base constitutes a bed plate 22 upon which are mountedthe principal operating elements of the device.

Supported within an opening formed in the top wall of the base 10 is anelectric motor 16 which is suitably secured to the base as by means of amounting bracket 27. and bolts 26. Current is supplied to the motor, asby means of a cable 28, and a conventional switch assembly is providedto control the motor circuit. The motor 16 serves to drive a grindingelement 46, preferably in the form of. a cylindrical grinding wheeladapted to' dres's' down the surface of a brake shoe lining.

. A hood having an open front 52 is removably "se cured to the base 10as by means of wing fastening studs 53, and substantially encloses thegrinding element 45. The interior of the hood communicates through aseries of passages (not shown) with a suction chamber and a dustcollection chamber (not shown) into which air and comminuted products ofabrasion are drawn.

A carriage 70 is slidably disposed on the upper surface of the bed plate22 for adjustable movement toward and away from the grinding element 46.The carriage is substantially fiat in shape, and is formed with a flatcircular turntable bed (Figs. -1 and 4) on which there is rotatablydisposed a turntable 76 adapted to support a workpiece holder 80. Theturntable 76 pivots about a turntable pivot axis established by a pivotpin 78 as explained more in detail hereinafter.

Means for accurately positioning the carriage 70 on the base 10 areprovided in the form of indexing and adjusting means, as, for example,the means disclosed and claimed in my heretofore mentioned copendingapplication. The external controls for these means comprise a knobprojecting from one side wall 14 of the base and constituting a part ofthe mechanism by which the car riage is adjustably positionable inpredetermined spacedapart index locations on the base, and an adjustingscrew 62 fixed to the forward end of the carriage 70 and constituting apart of the mechanism by which the carriage is accurately adjustableonthe base intermediate of the respective index locations.

A reference mark 66 provided on the carriage cooperates with an indexscale68 provided, for convenience. on a plate 69 attached to the sidewall 14 of the base 10 to indicate to the operator the indexed locationof the carriageonthe base, while a series of indicia provide a scale onthe circular'periphery of the adjusting screw 62 to cooperatewithreference marks on stationary portions of the carriage, and indicate thedistance the carriage has moved along the base from the indexinglocation in which the carriage'ispositio'ned.

The indexing 'locationsare so arranged as to establish spacedpredetermined positions of the carriage on the base, and, accordingly,to establish corresponding predetermined positions of the turntablepivot axis relative to the surface of the grinding element. In thepresent illustrated embodiment, the indexing locations are spacedone-half inch apart, and are so located as to determine positions oftheturntable pivot axis spaced progressively from the grinding element,ranging from 4 /2 to 8 inches therefrom. The index scale 68 is arrangedand marked as to indicate diameters corresponding to the respectiveradii which the indexing holes establish between the turntable pivotaxis and the grinding element. For example, when the reference mark 66registers with the indicium 11 (Fig. l) on the index scale 68, and theadjusting screw is at its ier'o point, the pivot axis of the turntableis exactly 5 /2 inches from the surface of the grinding element.Radius-indexing increments one-half inch in length have proved to besatisfactory for the present embodiment, inasmuch as new automotivebrake drums are commonly manufactured with diameters in one-inchmultiples. In processing a lining on a brake shoe for a drummanufactured with a diameter not a multiple of whole inches, or for adrum which has been machined off a whole-inches diameter, the adjustingmeans must be used to complement the indexing means for establishing thecorrect grinding radius. Accordingly, should a brake drum of 'amanufactured diameter of 11" have been machined to remove material .060inch in depth, the adjusting sc'rew must be manipulated so that theindex and adjusting scales together indicate a brake drum diameter of11.120 inches, or a distance of 5.060 inches between the turntable pivotaxis and the surface of the grinding element.

Means are provided for securely locking the carriage to the bed plate 22in any one of its adjusted positions, and for protecting the indexingand adjusting means from receiving any of the forces developed during a3 grinding operation. These means may take the form disclosed in myabove-mentionladen-pending, application, inwhich a rotatable thrust pin82 (Fig. '1) constitutes a part of'clamp.v means releasably biasing thecarriageand the base together.

Referring now to Fig. 4, theturntable. bed of the carriage 70 isprovided with a circular track or rail 90, while the turntable 76 isformed with a circular base 92 having an annular surface 94corresponding to and adapted to ride on the circular rail. The turntable76 also is formed with an. annular flange 96 which encompasses thecircular rail 90 and provides a seal or protection against ingress ofdust or other foreign material between the circular base 92 of theturntable 76 and the turntable bed.

A headed pivot pin 110, in the form of a shoulder bolt, extends throughand is secured to the carriage 70 centrally of the circular rail 90thereof, as by a nut .112, and passesthrough bosses 114 and 116 providedon the carriage 70 and on the turntable 76 respectively. The pivot pin110 serves to center the turntable 76 on the circular rail 90 whilepermitting turning movement of the turntable about the axis of the pivotpin, which is the turntable axis.

The turntable 76 includes an upstanding body 100 having a pair oftransversely spaced bearings 98 formed therein, each of which preferablyconsists of longitudinally spaced portions 98a and 98b formed in theforward and rear wall members of the upstanding body respectively.

A workpiece holder 120 is removably mounted on th turntable 76, andincludes a holder base 122 comprising a substantially flat shelf 124having a pair of cylindrical sockets 126 in its forward face 121. Thesockets have parallel axes, and are spaced apart transversely tocorrespond with the bearings 98 in the turntable. The sockets 126 areadapted to receiverespectively, corresponding ends of two elongate guiderods 130 which are fixed to the shelf 124, as by set screws 128, whenseated in the sockets. When thus seated, theguide rods extend forwardlyof the holder base, and are adapted to be received in the bearings 98 inthe turntable body 100.

1 The holder base 122 carries a projection 132 (Figs. 4

and 6) extending from its forward face 121 positioned to abut the head11% of the turntable pivot pin 110 when the guide rods are projectedthrough the bearings 93. The guide rods are of such length that theirforward ends 131 project slightly from the turntable body when the guiderods are inserted through the bearings until the projection 13?. of theholder base abuts the head of the turntable pivot pin.

A keeper bar 134 (Fig. 2) is provided as a means for preventing theguide rods and the holder base from sliding relative to the turntable.The keeper bar substantially takes the shape of a truncated T, and hasarms 136 adapted to enter annular grooves 138, one in the projectingforward end 131 of each guide rod 130. A thumb screw 140 is threadedthrough the keeper bar 134 intermediate the two arms 136 to bear againstthe forward wall of the turntable body. The force exerted by the thumbscrew 140 against the keeper bar 134 and the turntable body forward wallfirmly seats the projection 132 of the holder base in abuttingrelationship with the head 118 of the turntable pivot pin 110.

The holder base shelf 124 has an arm 142 (Figs. and 6) extendinglaterally therefrom upon which a pivot assembly 144 is adjustablypositionable. The arm is provided with an elongate slot 146 extendingtransversely of the axes of the guide rods, the slot being positionedsuch that its extended center line intersects the turntable pivot axis.The length of the slot and its lateral location relative to theturntable pivot axis are such as to permit adjustment of the position ofthe pivot assembly 144 throughout the entire range of movement requiredto accommodate in the workpiece holder. the standard range of sizes ofbrake shoes. The workpiece holder simulates-the actual brake assembly inrespect to the relative locations of the brake drum center and the fixedanchor for the shoe. A shallow elongate channel 148 concentricallyoverlies the slot 146 and is of greater length and width than the latterfor reasons hereinafter explained.

The pivot assembly 144 (Fig. 7) includes a cylindrical bushing 150having a hexagonal flange 152 on the upper end thereof. This bushing isdisposed vertically in the slot 146 with the hexagonal flange seating inthe channel 148 as to be slidable therein along the length of thechannel due tothe engagement of two opposed segments 153 of the flangewith the upstanding sides of the channel. When the hexagonal flange isproperly seated in the channel, the axis, of the cylindrical bushing 150will be parallel to the turntable pivot axis, while a plane containingboth axes will be perpendicular to the axes of the guide rods. "lhebushing 150 is of sufficient length to project through the slot 146, andis adapted to be firmly fastened in any desired position of ad ustmentalong the length of the slot by a nut 153 and washer 154, the formerbeing threaded onto the bushing. The bushing contains an axialcylindrical bore 155 within which an anchor pm 156 is slidably andpivotally recelved. The anchor pin has an enlarged head 158 which has adiameter adapted to be received firmly in the anchor guide recess of thebrake shoe to be ground, in order to permit accurate positioning of theshoe in the grinding device. in this connection, an anchor pin head .810inches in diameter will fit the most commonly used brake shoe. However,brake shoes are used which have recesses adapted to accommodate largeranchors. In or der to correctly position such a recess about anundersized anchor pin head, the anchor pin may be modified to provide asymmetrical base for the recesses. Accordingly, a generally rearwardfacing vertical fiat 300 is formed on the anchor pin head 301, this flatextending longitudinally of the cylindrical pin head to provide twosharp vertical edges against which the arcuate anchor guide recess canbe firmly seated as shown in Fig. 9. in order to properly center therecess about the anchor pin, the flat is located such that a radius ofthe arcuate recess which bisects that recess will lie substantially in aplane extending radially from the cylindrical anchor pin headperpendicularly to the flat. If the recess is either too small for theanchor pin head or is so oversize that the vertical flat will notprovide a firm seat therefor, it will be necessary to replace the anchorpin with one having a head of correct diameter.

A workpiece chuck 160 (see Fig. 4) is supported on the holder base forsliding movement relative thereto, and includes a frame 162 having agenerally U shape, with the U disposed on its side, extendingtransversely of the device, and opening toward the grinding element. Asthus disposed, the frame has upper and lower horizontal members or arms164 and 166. A pair of bosses 168 (Fig. 3) project from the uppersurface of the upper member 164 and are spaced apart transversely, thebosses bearing cylindrical bores 169 vertically therethrough in which apair of identical thrust pins 170 (Fig. 3) are slidably disposed. A pairof workpiece locater buttons 172, in the form of beaded pins, projectslightly from the upper face of the lower member 166, these pins beingconcentric with the thrust pins 170. Overlying the two thrust pins-is acap 174 which is provided with a recess 179 on its lower face into whichare received the upper ends of the thrust pins. Means for attaching thecap to the frame are provided in the form of a threaded stud 173paralleling the thrust pins and slidably projecting through the cap intothreaded engagement with a boss 171 formed on the upper member of theframe 162 intermediate of the bosses 168. The stud carries amanipulating knob 175 at its upper end to facilitate the advance orretraction of the threaded perv.

. 3' tion thereof. Disposed het-ween'the cap'and the-bosses 168 of theframe and on the portions of the thrust pins 170 therebetwe'en, area'p'airof helical 'springs176. These springs abut the upper surface ofthe bosses at "one end thereof and abut split Washers 1'77 fastened tothe upper portions of the thrust pins at the other ends of saidsp'ringssuchthat anyforce tending to'propelthe'thrust'pinsdownw'ardlyithrbughthe cylindrical bores inthe upper member of the frameis resisted by the springs. It will be seen that a'tu'r'n'ing of themanipulating knob will thread the stud intoth'e'frame andcause the capto force the thrust pins downwardly toward "the lo'c'a-ter' buttons. Aworkpiece, 'sucha's 'a'n automotive brak'e shoe BS, can befirm- 1y heldinthe chuck by tightening the manipulating knob to'the point where thewerkpie'ce is gripped 'between' the thrust pin'sand the locatrbuttor'fs.

Provision is 'rnad'e'torattachi'ng theehu'ck 160'to the holder baseshelf 124 for relative sliding movement thereb'e'tween, including anelongate slot 125 formed longit'u'dii'ia'llyin the shelf, 'the 'c'eritfline thereof extending substantially parallel to and intefine'diate theg'uide'rods 130'. A (Sap screv'v 127 of sha'nk diameter substantiallyless than the width of the'slot 12'5, forreasons hereinafter set forth,is projected 've'r' ieallyupward through the latter 'and'thre'ade'd intothe chuck. A Washer 129 is disposed betweefi -the head '133' of the capscrew and the bottofii or the'holderhasie shlf toprvrit the head or thecap screw'rroni assing into" or up through the slot. A spacer in theform of 'a'bushirig"123"of -a length slightly in' excess or thethickness 'dfnie shlfis' telescoped over the shank portion of the" capscrew. Theexternardiameter of this bushing also is substantially smaller'than'the width of'the slot 125 for reasons explained hereinafter, whilethe length of the' bushing permits theca s rew to chuck 160 with theanchor pin 156'on'the holder base arm 142. The pivot arm'is rigidlyfixed at one end, as by a set secr' ew20'3ywithin 'acyliridricalsocket202 in thechu'ck, and at the'other end slidably' projects through a bore204 in the head 158 of the anchorpin. A "clamp screw 206 is threadedinto the anchor pi'n axially thereof to bear against the pivot armportion disposed within the bore, and provides a means whereby the pivotarm can be released so'as to be slidable withinthe bore for adjustmentof theetfecti've length thereof, and then firmly secured in thatadjusted position. To provide a firm'seating of the clamp screw againstthe pivot arm, the pivot arm has a flattened portion 201 against whichthe clamp screw can bear. Once the clamp screw isfirmly screwed downagainst the pivot arm, the chuck'160 is secused to the holder base 122for pivotal movement about the anchor pin 156. It can beseen that thepivot arm extending from the chuck serves to support the anchor pinagainst any movement axially of bushing 150.

The extent of pivotal'movementof the chuck on the holder base islimitedby the length and width of'the longitudinal elongate slot 125 inthe holder base shelf 124, for it can be seen that thebushing-surroundedcap screw 12'? can travel only the arcuate path from one face of theslot 125 generally diagonally, relative to its center line, to the otherface. It is for the purpose of permitting the dlagonal movement of thebushing-surrounded cap screw across the width of the slot that the capscrew 127 and the bushing 123 are of diameter substantially less thanthe width of the slot.

Means are provided for attaching a feed screw 180 (Figs. 1 and 4) tothe'chuck, and take theform of a projection 182 extending from theforward wall thereof'and having a transverse recess 184'. The feed screwcomprises an elongate rod 19'2'terminating' in a substantiallyball-shaped rearmost end portion 186, with an annular reces's formed inthe rod adjacent and forwardly of the ball portion. The ball portion 186of the rod is disposed within'the transverse recess 184 of theprojection 182 and is retained in that recess by an overlying retainingblock 194 fastened to the frame of the chuck by cap screws 196". Whenthe block 194 is in position, the rod is restrained against longitudinalor axial movement by a li'p 185 of the recess.

'The feed screw 180 extends forwardly of the chuck 160 to overlie theforward end of the carriage 70, and is provided with threads 208throughout the major portiorr ot it's length. A handle 210 is secured onthe forward end of the feed screw 180 in order that an operator mayimpart rotational movements to the feed screw and also to oscillate thesame, as well as the turntable, from side to side. The threaded portion208 is adapted to be received in a half-nut 212pr'ovided on theturntable 76 having a pair of upstanding ears 214 which definethereb'etwe'en a semi-circular'threaded bore 216, the threads of whichare designed for cooperation with the threads 208 on the feed screw 180.

A'guid'e arch228 (Figs. 3 and 4) in the shape of an inverted Uupstanding from the holder base 122 straddles the feed screw adjacentthe 'ball portion 186, and serves the dual purpose of limiting'themovement of the feed screw to a pivoting movement in substantially avertical plane, and of rigidly'binding the feed screw against transversemovement when the latter'is depressed into threaded engagement with thehalf-nut 212. To this latter end, a spring-loaded, headed thrust pin 230is received transversely through a first arm 232 (Fig. 3) of the guidearch 228 and in a countersunk bore 234 therethrough. A hollow plug 236is threaded into-the major opening 235 of the countersunk bore, and hasan internal recess 238 in which is located a helical spring 239compressed therein and'against the'pin 230 to project the latter withinthe guide arch. The spring-loaded pin 230 is positioned to beartransversely against the feed screw 180 when the latter is in depressed,thread-engaged position Within the half-nut 212, and serves to bias thefeed screw against an opposing elongate boss 240 projecting within theguide arch from the second arm 242 thereof. The boss is of sufficientlength in a direction parallel to the axes of the guide rods 1350 toprovide a flat surface imparting to the feed screw a correspondingparallelism with the guide rod axes. The elongate boss 240, therefore,constitutes means'for maintaining the threaded portion of the feed screw180 in vertical alignment with the half-nut 212so that upon angulardepression of the feed screw in any position of the turntable thethreaded portion 208 will fall into register automatically with thehalf-nut 2 12.

Since'the feed screw 180,-byvirtue of its reception in the recess 184and withinthe guide arch 228 is pivoted for movement substantially in avertical plane, it will be seen that'the operator may at will lift thefeed screw out of the half-nut structure to disengage the same therefromand by applying a thrust or a pull to the feed screw 180, as the casemaybe, slide the chuck arcuately relative to the'holder base about theanchor pin 156 in a direction toward and away from the grinding element47. Such a'sliding movement of the chuck'by the application of a thrustor a pull to the feed screw provides a fast or a coarse adjustment forthe purpose of advancing a brake'shoe into initial grinding relationwith respect to the grinding element. When the lining of the brake shoehas been brought into close proximity to the surface of the grindingelement 47, a fine adjustment may be made by lowering the feed screw 1S0into'the half-nut '212for engagement between the threads thereof withthe threads 208 on the feedserew, after which rotation of the feedsc'r'ew about its longitudinal axis in one direction or the other willfeed the chuck 160, together with the brake sho'esupported thereon,toward the grinding element for grinding purposes.

shoe.

Means are provided for locating the pivot assembly 144, and thereforethe anchor pin 156, a predetermined distance from the axis of theturntable pivot pin 110 along the slot 146, and for positioning thepivot arm 200 on the anchor pin to establish a predetermined effectivelength of the pivot arm on which the chuck 160 will pivot about theanchor pin (see Figs. 3 and 6). These means include a first referencepin 246 fixedly upstanding from the holder base arm 142, and a gauge 248of predetermined shape for each given size and type of brake The firstreference pin is centered on the extended center line of the slot 146,and provides a convenient reference point fixed relative to theturntable pivot axis. The gauge 248 (Fig. 8) has a:first cylindricalbore 250 on a first end 245 adapted to receive therethrough the head 247of the first reference pin 246 and seats itself on 156 is adjusted to aposition in the slot 146 wherein the a head 158 isin register with thesecond bore 252 in the gauge 248. A shoulder 253 of height equal to thatof the shoulder 249 on the first reference pin head 247 is provided onthe anchor pin head 158 for seating the gauge 248.' The gauge 248 thusprovides a means by which the anchorpin 156 is easilylocated in apredetermined position relative to the turntable pivot axis. Once thegauge is seated on both the first reference pin and the anchor pin head158, the anchor pin may be firmly fastened in place by a tightening ofthe nut 153 on the bushing 150.

The gauge 248, when seated on both the first reference pin 246 and theanchor pin head 158, serves also to establish a predetermined effectivelength for the pivot arm 200, in that the other end 251 of the gaugeextends beyond the second bore 252 a predetermined distance. This end251 is of substantial width to provide an abutment edge 255 againstwhich is seated a second reference pin 260 fixedly upstanding from theend of the pivot arm 200. Since the chuck is positioned rearwardly ofthe turntable axis, and the anchor pinv is positioned transverselythereof, the pivot arm 200 joining the chuck and anchor pin takes anangular direction relativeto both the longitudinal and transverseextents of the device. Accordingly, the abutment end 251 of the gauge248 may be angularly disposed from the center line direction between thebores 258 and 252. When the second reference pin 260 and the end 251 ofthe gauge 248 are in contact, and the gauge is otherwise properlyseated, on the first reference pin and the anchor pin head, the pivotarm 200 will have a predetermined effective length between the anchor.pin 156 and the chuck 160. Brake drumsmay have varying radii ofcurvature, and the assemblies therefor may havefixed anchors positioneddifierently from one another relativeto their spindles, Accordingly, adifferent gauge is provided for the shoe of each differently dimensionedand designed assembly, each gauge having apredetermined length betweencenters of the first reference and the anchor pin bores. Thebore-to-bore length is predetermined for each different brake drum sothat the total of that length and the distance between the turntablepivot axis and the first reference bore is equal to the distance betweenthe fixed anchor and the spindle of the brake drum whose shoe is to beprocessed. Theuse of a first reference pin and an elongate anchor pinslot extending radially from the turntable pivot axis thus facilitatesthe positioning of the anchor pin on the holder base arm.

Referring now to Fig. 6, it will be clear that once the anchor pin ispositioned on the holder base arm, the pivotal position for a brake shoerelative to the turntable is also fixed. Adjustment of the effectivelength of the pivot arm positions the chuck so that it may receive andhold a brake shoe of any radius of curvature in operat ng proximity tothe grinding element and substantially symmetrically thereto.Additionally, the force exerted be tween the grinding element and thebrake shoe is borne by the chuck, which firmly holds the brake shoeagainst slipping, chattering or erratic movement while the shoe is incontact with the grinding element.

The lengths of the two elongate slots 146 and (see Fig. 6) limit therange of sizes of brake shoes that can be received by the device, butthe slots and the gauge means for positioning the anchor pin relative tothe turntable axis as well as for establishing a predetermined effectivelength of the pivot arm on that anchor pin are adapted to enableprocessing of all standard sizes of brake shoes.

A projection 178 (Figs. 5 and 6) is provided on the rearward face ofeach of the frame members 164 and 166, these projections extending"rearwardly of the chuck frame to provide two seats in a perpendicularplane against which the rim of a workpiece, such as an automotive brakeshoe, is positioned, while the ancho'r'pin head 158 provides a thirdseat for the brakeshoe. These three seats are reference pointsestablishing a very positive and firm means of positioning a brake shoeworkpiece in the grinding device.

To illustrate the operation of the device in dressing down the lining Lof a standard fixed anchor brake shoe BS it may be assumed that a brakeshoe is being processed for an ll-inch brake drum in new condition.Accordingly, it is necessary that an accurate 5 /2 inch pivot radius beset for the turntable in order to grind the lining L to a true arematching that of the brake drum. In order to set the arcuate radius, theoperator must first free the carriage 70 for sliding movementlongitudinally on the base 10. This is accomplished by the release ofthe clamp means thrust pin 82, and by the lateral retraction of the knob60 from locking engagement with the indexing mechanism (not shown). Thedetermination of the location in which the carriage is positioned on thebase the correct distance from the grinding element is accomplished byuse of the reference mark 66 and the scale 69 on the base. When the markis in register with the desired indicium, "11 in the presentillustration, the knob 60 is depressed to index-lock the carriage on thebase. A 5 /2 inch pivot radius for the surface" of the lining L has thusbeen set, and no movement of the adjusting screw 62 off its zero pointshould be made for the brake shoe of this illustration since its brakedrum is an accurate 11 inches in diameter. The carriage-indexing andadjusting mechanism is next protected from receiving the forcesdeveloped during the grinding by actuating the clamp means thrust pin 82to frictionally lock the carriage onto the base at the correctlyestablished location. These clamp means will thereafter receive anyforces developed during the grinding operation, rather than the indexingmeans or the adjusting screw.'

The correct locating of the pivot assembly 144 on the arm of the holderbaseis accomplished by means of a selected gauge 248 corresponding tothe particular brake shoe to be ground. The pivot assembly 144 isreleased for sliding movement on the arm by loosening the nut 153 fromthe bushing 150. Thereupon the gauge 248 is placed on the firstreference pin 246 so that the latter pin penetrates the bore 250 and thegauge seats itself on the shoulder 249 of the pin. The pivot assembly ismoved along the slot 146 until the anchor pin head 158 c is in registerwith and penetrates the second bore 252 in the gauge. Once the gauge isseated on both the shoulder 249 of the first reference pin and theshoulder 253 of the anchor pin head 158, the nut 153 is tightened on thebushing to fasten the pivot assembly firmly on the holder base arm.

The effective length of the pivot arm 200 is properly set for theparticular brake shoe to be ground by backing off the clamp'screw 206from contact with the planar surface 201 of the pivot arm, and bysliding the pivot arm within the'cylindriqal bore 204 in th anchor pin11 head until the second reference pin 260 abuts the end 251 of thegauge 248. When the pivot arm is so positioned, it is firmly fixedrelative to the anchor pin by tightening down the clamp screw 206.

The chuck 168 is prepared for the brake shoe to be ground by backing offthe thrust pins 170 from the locater buttons 172. This is accomplishedby rotation of the manipulating knob 175, and therefore the stud 173, toeffect a raising of the cap 174. This, in turn, permits the helicalsprings 176 to withdraw the thrust pins away from the workpiece locaterbuttons. When the thrust pins are sufficiently removed from theworkpiece locater buttons, the brakeshoe to be ground is insertedtherebetween until the rim R of the brake shoe abuts both of theprojections 178 of the chuck 160 and the anchor recess AR accommodatesthe anchor pin head 158. The brake shoe is fastened in this position byscrewing the stud 173 further into the frame 162 until the thrust pins170 firmly bias the flange F of the brake shoe between them and thelocater buttons 172. Due to the vertical alignment of both projections178, one with the other,

and the horizontal alignment of both locater buttons 172 one with theother, the brake shoe is seated as to have its pivot axis correctlydisposed parallel to the axis of the grinding wheel.

The brake shoe is brought into close proximity to the grinding wheelrapidly by the coarse advancing means. This is accomplished by swingingthe feed screw 180 upwardly out of engagement with the half nut 214,whereupon a forward thrust on the feed screw will cause the workpiecechuck 160, together with the brake shoe that it holds, to move towardthe grinding element pivotally about the anchor pin 156. When thesurface of the lining L is in close proximity with the grinding element,the accurate advancing-means are employed to complete the advance of theworkpiece into the grinding element. This is accomplished by depressingthe feed screw 180 pivotally about its ball portion 186 to cause itsthreaded portion 208 to engage the threads 216 in the half-nut 214. Thefeed screw 180 is then firmly held between the halfnut 214 and the guidearch 228, and by its rotation about its longitudinal axis advances thechuck 160 in a finely controlled manner by means of the threadedengagement between the feed screw and the half-nut 214. Inasmuch as theradius of curvature of the arcuate surface to be processed is fixed bythe location of the turntable axis and corresponds to the distancebetween the turntable axis and the closest point thereto on the grindingwheel, the brake shoe is advanced into the grinding wheel until theentire arcuate extent of the lining L will be dressed down uponoscillation of the entire turntable, workpiece holder assembly, andbrake shoe as a unit, by oscillatory manipulation of the handle 219.

When a brake drum has been machined to either remove scorings on theinner surface thereof or to bring the inner surface thereof to a truecircular shape, the drum will no longer have a diameter of standardwhole-inches dimension, such as, for example, 11 inches. The presentdevice is equally well adapted to process the lining of the brake shoefor this enlarged brake drum, the only additional adjustment necessarybeing that of advancing the adjusting screw so that the turntable radiusestablished between the turntable axis and the surface of the grindingwheel is increased by the difference between the initial or standardradius of the brake drum and its rebored radius. Since the position ofthe fixed anchor in the brake drum relative to the drum spindle is thesame as in the drum when in new condition, no adjustment of the anchorpin on the holder base arm need be made, and the brake shoe can beground as heretofore described in connection with a brake shoe for a newor standard size brake drum.

'While the present invention is particularly well-adapted to and hasbeen described in connection with grinding linings of brake shoes of thefixed anchor type, the invention is not limited to such a use, for agrinding device incorporating the principles of this invention canaccommodate equally well brake shoes of the adjustable anchor type. Aswhen dressing down the linings of a fixed anchor brake shoe, a gauge 248must be selected for use, which corresponds to the particular brake shoeto be ground. An adjustable anchor shoe is positioned in the chuck inthe same manner as a fixed anchor shoe, utilizing the projections 178 ofthe chuck 160 and the anchor pin head as reference seats for the shoerim and the brake shoe anchor recess. The shoe is pivotally advanced inthe manner of fixed anchor shoes toward the grinding element, and swungthrough an arc of engagement therewith. It can be seen that thecapability of this grinding device of processing both types of brakeshoes, adds considerably to the chiciency and convenience of its use,particularly in the herein discussed automotive brake shoe field.

It can be seen that the present invention substantially duplicates thebrake drum for a fixed anchor brake shoe being ground. The turntablepivot axis and the workpiece holder anchor pin correspond respectivelyto the drum spindle and the drum anchor. The grinding element edgeclosest to the turntable pivot axis corresponds to a line on the drumbraking surface, while the circular extent of that drum surface isduplicated, not by rotation of the grinding element edge around theturntable and about the turntable pivot axis, but rather by rotation ofthe turntable, with its supported workpiece holder and brake shoe, aboutthe turntable pivot axis. The contour of the drum surface is representedby the path the closest edge of the grinding element describes relativeto the turntable periphery. It can be further seen that as the shoe isadvanced pivotally into that path, the lining of the shoe will be groundto the contour of the brake drum.

The elongate slot 146 in which the anchor pin is slidably positionableextends transversely of the axes of the guide rods 131, and thereforethe anchor pin is always located laterally from the axial direction ofthe application of force by the feed screw 180. Such a structure makespossible the advance of the shoe pivotally about the anchor pin by theapplication of a feed screw force in substantially the same manner as abraking force pivots the shoe within the drum therefor. The combinationof the elongate transverse slot and the first reference pin a fixeddistance from the turntable pivot axis provides a novel and convenientmeans of locating the anchor pin a predetermined distance from theturntable pivot axis, and enables the use of a gauge 248 convenient forthat purpose.

The elongate slot extending longitudinally relative to the turntablemakes possible not only the arcuate movement of the chuck cap screw 127therein as the chuck and workpiece are pivoted about the anchor pin, butalso the longitudinal adjustment of the chuck and workpiece toward oraway from the grinding element as the effective length of the pivot arm200 is lengthened or shortened. The proper position of the chuckrelative to the grinding element is dependent on whether the workpieceis of relatively large or small radius of curvature and therefore ofrelatively flat or of sharp arcuate contour. It will be apparent thatthe surface of a workpiece of relatively fiat contour will not projectfrom the chuck to the extent the surface of a workpiece of relativelysharp contour projects, and that the chuck for the workpiece of flatcontour must itself be farther advanced to the grinding element to establish grinding contact between that element and the workpiece.

The bushing-surrounded chuck cap screw 127 is free to move arcuately inthe longitudinal slot 125 (Fig. 6) until the bushing-surrounded capscrew abuts a face of the slot. Since the cap screw is rigidly connectedto the chuck, which in turn firmly holds a brake shoe BS, it can be seenthat any advancing movement of the cap screw 127 is attended by movementof the brake shoe. The brake shoe is preferably advanced to a positionwhere the lining L of the shoe will be in engagement with the grindingelement throughout the entire extent of the lining when the brake shoeis pivoted with the turntable. When the brake shoe is pivoted with theturntable and in contact with the grinding element, material will beground from the lining tapering from a greatest depth of removal in anarea generally intermediate of the lining ends toward areas of leastdepth of removal adjacent those ends.

The pivot arm 200 is made to be slidably positionable on the anchor pinto provide adjustment of the efiective length of the former. Thisadjustment is required to accommodate the shoes for drums of varyingdiameters, for it can be seen that as the distance from the turntablepivot axis to the grinding element is increased to simulate largerdiameter drums, and as the anchor pin is positioned laterally fartherfrom the turntable pivot axis to simulate the position of the anchor inthe larger drums, so also must the pivot arm, corresponding to ahypotenuse of these two lengths, be increased to correctly position thechuck and workpiece relative to the grinding element.

It will be apparent that this device is simple in construction and canbe economically manufactured. At the same time, however, the device isrugged and sturdy, free from any requirement of delicate adjustment, andfree from easily broken or deformed parts which might requirereplacement.

I claim:

1. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an armextending laterally from said holder base, an anchor pin on said arm, aworkpiece chuck slidably mounted on said holder base for arcuatemovement relative thereto about said anchor pin toward and away from thegrinding element, and a pivot arm connecting said chuck and said anchorpin.

2. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinupstanding from said holder base, a workpiece chuck, a pivot armconnecting said chuck and said anchor pin, and means slidably mountingsaid chuck on said holder base for arcuate movement of said chuckrelative to said holder base toward and away from the grinding element,said mounting means including an elongate slot in said holder baseextending generally toward and away from said grinding element, a screwprojected through said slot and threaded into said chuck, and acylindrical spacer on said screw, said spacer being of substantiallysmaller external diameter than the width of said slot.

3. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an armextending laterally from said holder base, an anchor pin positionable ina plurality of locations on said arm, a workpiece chuck slidably mounted.on said holder base for arcuate movement relative thereto about saidanchor pin toward and away from the grinding element, a pivot armconnecting said chuck and said anchor pin, and means for adjusting theefiective length of said pivot arm.

4. A workpiece holder for a grinder of the type having a base, agrinding element rotatably mounted on the base, a carriage mounted onthe base for sliding move- I ment toward and away from the grindingelement, and

a turntable carrying an open half-nut and rotatably mounted on thecarriage on a pivot axis parallel with the axis of rotation of thegrinding element, said workpiece holder comprising a holder base rigidlymounted on the turntable, an anchor pin upstanding from said holderbase, a workpiece chuck slidably mounted on said holder base for arcuatemovement relative thereto about said anchor pin toward and away from thegrinding element, a pivot arm connecting said chuck and said anchor pin,and a feed screw attached to said chuck rotatably relative thereto andswingably relative thereto into and out of threaded engagement with thehalf-nut, said feed screw constituting a thrust rod for manual movementof said chuck relative to said holder base when said feed screw isdisengaged from the half-nut and constituting screw means for accuratemovement of said chuck relative to said holder base upon rotation of thefeed screw when the latter is in threaded engagement with the half-nut.

5. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable carrying an open half-nut and rotatably mounted on saidcarriage, said workpiece holder comprising a holder base rigidly mountedon said turntable, an anchor pin upstanding from said holder base, aworkpiece chuck slidably mounted on said holder base for arcuatemovement relative thereto about said anchor pin toward and away from thegrinding element, a pivot arm connecting said chuck and said anchor pin,a feed screw attached to said chuck as to be rotatable relative theretoand swingable relative thereto into and out of threaded engagement withthe half-nut, and a guide arch upstanding from said holder base andstraddling said feed screw, said feed screw constituting a thrust rodfor manual movement of said chuck on said holder base when said feedscrew is disengaged from the half-nut and constituting screw means foraccurate movement of said chuck on said holder base upon rotation ofsaid feed screw when the latter is in threaded engagement with thehalf-nut, said guide arch holding said feed screw against transversemovement when the latter is in engagement with the halfnut andvertically aligning said feed screw with the halfnut when the feed screwis depressed toward threaded engagement therewith.

6. A workpiece holder for a grinder of the type having a base, agrinding element rotatably mounted on the base, a carriage mounted onthe base for sliding movement toward and away from the grinding element,and a turntable rotatably mounted on the carriage on a pivot axesparallel with the axis of rotation of the grinding element, saidworkpiece holder comprising a holder base rigidly mounted on theturntable, an anchor pin upstanding from said holder base, a workpiecechuck slidably mounted on said holder base for arcuate movement relativethereto about said anchor pin toward and away from the grinding element,a pivot arm connecting said chuck and said anchor pin, a feed screwhaving a ball-like end portion, and means rotatably and swingablyattaching said feed screw to said chuck, said attaching means includinga projection extending from said chuck, a recess in said projection forreceiving said ball-like end portion, and a retaining block fixed tosaid chuck and holding said ball-like end portion in said recess, saidfeed screw constituting a thrust rod for manual movement of said chuckrelative to said holder base when said feed screw is disengaged from thehalf-nut and constituting screw means for accurate movement of saidchuck relative to said holder base upon rotation of the feed screw whenit is in threaded engagement with the half nut. 7. A workpiece holderfor a grinder of the type having a base, a grinding element supported onthe base, a carriage mounted on the base for sliding mo ement toward andaway from the grinding element, and a turntable rotatably mounted on thecarriage and containing a pair of transversely spaced cylindrical bores,said workpiece holder comprising a holder base, means removably mountingsaid holder base on the turntable, said mounting means including a pairof transversely spaced longitudinally extending guide rods projectingfrom said holder base and slidably received in the turntable bores, andmeans for rigidly clamping said guide rods in the bores, an anchor pinupstanding from said holder base, a workpiece chuck slidably mounted onsaid holder base for arcuate movement relative thereto about said anchorpin toward and away from said grinding element, and a pivot armconnecting said chuck and said anchor pin.

8. The invention of claim 7 wherein said guide rods project through saidbores forwardly of said turntable, and said means rigidly clamping saidguide rods in the bores include an arcuate groove in the projecting endof each of said guide rods, a keeper bar engaging both of said arcuategrooves, and means acting between said keeper bar and the turntable forholding the guide rods against axial movement relative to the turntable.

9. A workpiece holder for a brake shoe grinder of the type having abase, a grinding element supported on the base, a carriage mounted onthe base for sliding movement toward and away from the grinding element,and a turntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base mounted on the turntable, an anchor pinupstanding from said holder base, a workpiece chuck slidably mounted onsaid holder base for arcuate movement relative thereto about said anchorpin toward and away from the grinding element, and a pivot armconnecting said chuck and said anchor pin, said workpiece chuckincluding a frame, a pair of transversely spaced pads fixedly supportedby said frame and having brake shoe flange-engaging surfaces lying in aplane and disposed to engage one face of the flange of a brake shoe inthe holder, a pair of pins slidably projectable through said frame inregister with said pads and into abutment with the other face of theflange of the brake shoe in the holder, a cap overlying both of saidpins, a stud projected through said cap intermediate of said pins andthreaded into said frame, a manipulating knob on the end of said stud,and spring means urging said pins away from said pads.

10. A workpiece holder for a brake shoe grinder of the type having abase, a grinding element supported on the base, a carriage mounted onthe base for sliding movement toward and away from the grinding element,and

a turntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base mounted on the turntable, an anchor pinupstanding from said holder base, a workpiece chuck slidably mounted onsaid holder base for arcuate movement relative thereto about said anchorpin toward and away from the grinding element, and a pivot armconnecting said chuck and said anchor pin, said workpiece chuckincluding a frame, a pair of transversely spaced pads fixedly supportedby said frame and having brake shoe flange-engaging surfaces lying in aplane and disposed to engage one face of the flange of a brake shoe inthe holder, a pair of pins slidably projectable through said frame inregister with said pads and into abutment with the other face of theflange of the brake shoe ,in the holder, a cap overlying both of saidpins, a stud projected through said cap intermediate of said pins andthreaded into said frame, a manipulating knob on the end of said stud,spring means urging said pins away from said pads, and a brake shoerim-engaging abutment projecting from said frame toward the grindingelement.

11. A workpiece holder for a brake shoe grinder of the type having abase, a grinding element supported on the base, a carriage mounted onthe base for sliding movement toward and away from the grinding element,and a turntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base mounted on the turntable, an anchor pinupstanding from said holder base, a workpiece chuck slidably mounted onsaid holder base for arcuate movement relative thereto about said anchorpin toward and away from the grinding element, and a pivot armconnecting said chuck and said anchor pin, said workpiece chuckincluding a frame, a pair of transversely spaced pads fixedly supportedby said frame and having brake shoe flange-engaging surfaces lying in aplane and disposed to engage one face of the flange of a brake shoe inthe holder, a pair of pins slidably projectable through said frame inregister with said pads and into abutment with the other face of theflange of the brake shoe in the holder, a cap overlying both of saidpins, a stud projected through said cap intermediate of said pins andthreaded into said frame, a manipulating knob on the end of said stub,spring means urging said pins away from said pads, and a pair ofvertically spaced abutments projecting from said frame toward thegrinding element and having brake shoe rim-engaging surfaces lying in aplane perpendicular to the flange-engaging surfaces of said pads.

12. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinpositionable in a plurality of locations on said holder base along aline perpendicular to the line of movement of the carriage and passingthrough the axis of rotation of the turntable, a workpiece chuckslidably mounted on said holder base for arcuate movement relativelythereto about said anchor pin toward and away from the grinding element,a pivot arm connecting said chuck and said anchor pin, and means forpositioning said anchor pin in any of its said locations on said holderbase and for adjusting the effective length of said pivot arm.

13. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinassembly positionable in a plurality of locations on said holder base, aworkpiece chuck slidably mounted on said holder base for arcuatemovement relatively thereto about said anchor pin assembly toward andaway from the grinding element, a pivot arm connecting said chuck andsaid anchor pin assembly, and means for positioning said anchor pinassembly in a predetermined location on said holder base and foradjusting the effective length of said pivot arm, said means includingan elongate slot in the holder base for guiding the movement of saidanchor pin assembly, said anchor pin assembly including a headed andthreaded cylindrical bushing slidably projected through said slot, a nutholding said bushing in said slot, an anchor pin slidably carried withinsaid bushing, an enlarged head on said anchor pin, a transversecylindrical bore in said head for slidably accommodating said pivot arm,said pivot arm supporting the anchor pin against axial movement withinsaid bushing, and means for releasably fastening said pivot arm to saidanchor pin head.

14. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinassembly positionable in a plurality of locations on said holder base, aworkpiece chuck slidably mounted on said holder base for arcuatemovement relatively thereto about said anchor pin assembly toward andaway from the grinding element, a pivot arm connecting said chuck andsaid anchor pin assembly, and means for positioning said anchor pinassembly in a predetermined location on said holder base and foradjusting the effective length of said pivot arm, said means includingan elongate slot in the holder base for guiding the movement of saidanchor pin assembly and a shallow channel concentrically overlying saidslot, said anchor pin assembly including a threaded cylindrical bushing,a polygonal head on said bushing, said bushing projecting through saidslot and said polygonal head slidably supported within said channel, anut threaded on said bushing to hold said bushing in said slot, ananchor pin slidably carried within said bushing, an enlarged head onsaid anchor pin, a transverse cylindrical bore in said anchor pin headfor slidably accommodating the pivot arm, said pivot arm supporting theanchor pin against axial movement within said bushing, and means forreleasably fastening said pivot arm to said anchor pin head.

15. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinslidably adjustable on said holder base along a line perpendicular tothe line of movement of said carriage and passing through the axis ofrotation of the turntable, a workpiece chuck slidably mounted on saidholder base for arcuate movement relative thereto about said anchor pintoward and away from the grinding element, a pivot arm fixed at one endto said chuck and slidably carried by said anchor pin at another end,means for positioning said anchor pin in any of its said locations onsaid holder base and for positioning said pivot arm on said anchor pin,said means establishing a predetermined radius of and positioning thecenter for the arcuate movement of said chuck.

16. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable mounted on the carriage and rotatable about an axis, saidworkpiece holder comprising a holder base rigidly mounted on theturntable, an anchor pin positionable in a plurality of locations onsaid holder base, a workpiece chuck slidably mounted on said holder basefor arcuate movement relatively thereto about said anchor pin toward andaway from the grinding element, a pivot arm connecting said chuck andsaid anchor pin, and means for establishing a predetermined radius ofand positioning the center for the arcuate movement of said chuck, saidmeans including a gauge positioning said anchor pin on said holder basea predetermined distance from said turntable axis and positioning saidpivot arm on said anchor pin to establish a predetermined effectivelength for said pivot arm.

17. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage mounted on the basefor sliding movement toward and away from the grinding element, and aturntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base rigidly mounted on the turntable, an anchor pinpositionable in a plurality of locations on said holder base, aworkpiece chuck slidably mounted on said holder base for arcuatemovement relatively thereto about said anchor pin toward and away fromthe grinding element, a pivot arm connecting said chuck and said anchorpin, and means for positioning said anchor pin in a predeterminedlocation on said holder base and for adjusting the effective length ofsaid pivot arm, said means including a first reference pin fixedlyupstanding from the holder base, a second reference pin fixedlyupstanding from the end of the pivot arm adjacent said anchor pin, anelongate slot in the holder base for guiding the move ment of saidanchor pin, and a gauge adapted to be mounted on one end thereof on saidfirst reference pin and to be mounted at a central portion thereof onsaid anchor pin when said anchor pin is moved along the slot to apredetermined distance from said first reference pin, the second end ofsaid gauge providing an abutment for said second reference pin apredetermined distance from said anchor pin.

18. A workpiece holder for a brake shoe grinder of the type having abase, a grinding element supported on the base, a carriage mounted onthe base for sliding movement toward and away from the grinding element,and a turntable rotatably mounted on the carriage, said workpiece holdercomprising a holder base mounted on the turntable, an arm extendinglaterally from said holder base, an anchor pin positionable in aplurality of locations on said arm, said anchor pin being adapted toengage the anchor recess of a brake shoe when the latter is positionedin the holder, a workpiece chuck slidably mounted on said holder basefor arcuate movement relative thereto about said anchor pin toward andaway from the grinding element, a pivot arm adjustable in effectivelength connecting said chuck and said anchor pin, said workpiece chuckincluding a frame, a pair of transversely spaced pads fixedly supportedby said frame and having brake shoe flange-engaging surfaces lying in aplane and disposed to engage one face of the flange of a brake shoe inthe holder, a pair of pins slidably projectable through said frame inregister with said pads and into abutment with the other face of theflange of a brake shoe in the holder, a cap bearing againstcorresponding ends of both of said pins, a stud projected through saidcap intermediate of said pins and threaded into said frame, amanipulating knob on the end of said stud, spring means urging said pinsaway from said pads, and means for positioning said anchor pin in apredetermined location on said holder base arm and for adjusting theeffective length of said pivot arm, said means including a firstreference pin fixedly upstanding from said holder base arm, a secondreference pin fixedly upstanding from the end of said pivot arm adjacentsaid anchor pin, an elongate slot in said holder base arm for guidingthe movement of said anchor pin, and a gauge adapted to be mounted onone end thereof on said first reference pin and to be mounted at acentral portion thereof on said anchor pin when said anchor pin is movedalong the slot to a predetermined distance from said first referencepin, the second end of said gauge providing an abutment for said secondreference pin a predetermined distance from said anchor pin.

19. A workpiece holder for a grinder of the type having a base, grindingelement supported on the base, a carriage slidable on the base towardand away from the grinding element and a turnable mounted on the basefor pivotal movement about an axis on the axis of movement of thecarriage, said holder comprising a holder base rigidly secured to theturntable, a brake shoe clamp slidable in an are on said holder base ina direction toward and away from the grinding element, and adjustablemeans for locating the position of the center and determining the radiusof movement of said clamp including a radius arm rigidly projecting fromsaid clamp, a pin for engagement by the anchor pin recess of a brakeshoe in said clamp, said pin being located on a line perpendicular tothe axis of movement of said carriage and passing through the pivot axisof said turntable and adjustable along said line toward and away fromthe axis of said turntable and means for adjustably connecting said armto said pin at different positions along said arm to thereby vary theeffective length of said arm from said clamp to said pin.

20. A workpiece holder for a grinder of the type having a base, agrinding element supported on the base, a carriage slidable on the basetoward and away from the grinding element and a turntable mounted on thebase for pivotal movement about an axis on the axis of movement of thecarriage, said holder comprising a holder base rigidly secured to theturntable, a brake shoe clamp slidable in an are on said holder base ina direction toward and away from the grinding element, and adustablemeans for locating the position of the center and determining the radiusof movement of said clamp including a radius arm rigidly projecting fromsaid clamp, 21 pin for engagement by the anchor pin recess of a brakeshoe in said clamp, said pin being located on a line perpendicular tothe axis of movement of said carriage and passing through the pivot axisof said turntable and adjustable along said line toward and away fromthe axis of said turntable, means for adjustably connecting said arm tosaid pin at different positions along said'arm to thereby vary theeffective length of said arm from said clamp to said pin, and a gaugeremovably disposed on said pin and having portions extending along saidperpendicular line and along the axis of said radius arm for determiningthe position of said pin and the effective length of said radius arm.

21. A workpiece holder for a grinder of the typehaving a base, agrinding element supported on the base, a. carriage slidable on the basetoward and away from the grinding element and a turntable mounted on thebase for pivotal movement about an axis on the axis of movement of thecarriage, said holder comprising a holder base rigidly secured to theturntable, a brake shoe clamp slidable in an are on said holder base ina direction toward and away from the grinding element, and adjustablemeans for locating the position of the center and --determining theradius of movement of said clamp including a radius arm rigidly.lp'rojecting from said clamp, a pin for engagement by "the anchor pinrecess of a brake shoe in said clamp, said pin being located in a lineperpendicular to the axis of movement of said carriage and passingthrough the pivot axis of said turntable and adjustable along said linetoward and away from the axis of said turntable, means for adjustablyconnecting said arm to said pin at different positions along said arm tothereby vary the effective length of said arm from said clamp to saidpin, an abutment on said holder base between said pin and said pivot, anabutment on that portion of said arm which extends on the other side ofsaid pin from said clamp, and a gauge removably disposed on said pin'andhaving a por tion abutting the abutments in said holder base and on saidarm respectively for determining the position of said pin and theefiective length of said radius arm.

References Cited in the file of this patent UNITED STATES PATENTS675,609 Pashl'ey 'June 4, 1901 1,095,338 Mallory May 5, 1914 1,287,091Pearsen Dec. 10, 1918 2,098,267 Weihampel Nov. 9, 1937 2,289,693 BlazekJuly 14, 1942 2,325,826 Barrett Aug. 3, 1943 2,715,799 Billeter Aug. 19,1950

